Patent Grant
7187334
This application is related to an application filed concurrently herewith, entitled “Tapered Slot Feed for an Automotive Radar Antenna,” U.S. application. Ser. No. 10/978,779, now pending which is incorporated herein by reference in its entirety.
This invention relates to an antenna structure having a patch array antenna feed in conjunction with a parabolic dish, particularly useful in a collision detection system in a vehicle.
Automotive technologies continually strive to make vehicles safer. In one aspect of vehicle safety, it is known to provide a vehicle with means to detect potential collisions and to take appropriate actions to avoid the same. For example, vehicles have been equipped with numerous types of sensors (e.g., infra-red sensors) which are able to broadcast radiation towards a potential obstacle (a tree, building, or another vehicle for example), receive radiation reflected from that obstacle, and determine that obstacle's distance and hence its potential as a collision hazard.
A developing technology in this area comprises antenna structures operating at or near 77 GHz frequencies. Such antenna structures include the ability to transmit and detect reflected 77 GHz radiation, and thus may be referred to as transceivers. A simple illustration of such a transceiver 12 mounted in a vehicle 10 is illustrated in
As noted earlier, the beam is swept (i.e., through angle θ) in any number of well known ways, for example, by causing the parabolic dish 16 to oscillate back and forth. Because such oscillation schemes are well known and not particularly important in the context of the invention, such details are not shown. However, it suffices to say that the dish 16 can be made to oscillate with respect to the housing 14 by mounting it thereto with springs or dampers to allow the dish to swivel, and by cyclically powering solenoids within the housing 14 to swivel the dish 16 by electromagnetic force.
Further details concerning the foregoing concepts and transceiver structures and controls can be found in U.S. Pat. Nos. 6,542,111; 6,646,620; 6,563,456; and 6,480,160, which are incorporated herein by reference in their entireties.
A major drawback to the collision detection transceiver 12 of the type illustrated is its cost, particularly as it related to the horn antenna 18. As a three-dimensional waveguide, the horn antenna is generally rather complex to design and manufacture, as the angles, lengths and the other various dimensions of the waveguide must be specifically tailored to give optimum performance for the radiation 20 (i.e., at 77 GHz) in question. This accordingly adds significant cost to the transceiver 12, which generally hampers use of the transceiver in vehicles that generally cannot be labored with substantial add-on costs. Moreover, from a functional standpoint, the use of the horn antenna adds additional structural complexity to the overall design of the transceiver assembly, as it essentially “sticks out” of the assembly, must be precisely coupled to the PCB 22, is susceptible to damage and misalignment, etc.
In short, room exists to improve upon existing vehicular collision detection transceivers, and this disclosure presents solutions.
In one embodiment, an improved transceiver assembly for a vehicle capable of detecting potentially hazardous objects is disclosed. The transceiver assembly comprises a patch array feed antenna having an array of a plurality of patches for generating a beam and for detecting the beam as reflected from the potential hazards. The antenna is formed in or on a housing which also contains a parabolic dish that oscillates to sweep the beam of radiation towards the potential hazards outside of the vehicle. In a preferred embodiment, approximately 77 GHz radiation is generated from and detected by the antenna.
The antenna of the transceiver assembly is preferably located at a focus of a parabolic surface of the dish, and is formed on a printed circuit board (PCB). The PCB can include a ground plane underneath the patches of the antenna, and can include additional circuitry necessary to operate the antenna. The antenna may be integral with the housing, formed on the housing, positioned within the housing, or at least partially exposed through the housing, so long as the loss of signal through any materials present on the assembly is minimized.
The patches of the antenna are preferably located at different positions on the antenna in a manner to preferentially steer the generated beam toward the dish, and are all connected to a common feed. By slightly altering the lengths of the feedlines to the patches, the phases of the various patches can be altered, with the overall effect being that the beam generated by the antenna can be generally steered toward the parabolic dish at an acute angle of incidence with respect to a plane of the patches.
The transceiver assembly is preferably mounted to or within a vehicle, such as in its bumper. The reflected signals can be transformed into a signal indicative of the potential hazard, which may in turn be sent to a vehicle communication bus to reduce a speed of the vehicle in a cruise control application, for example. Alternatively, the signal indicative of the potential hazard can be broadcast to the user, either audibly, visually, or both.
Embodiments of the inventive aspects of this disclosure will be best understood with reference to the following detailed description, when read in conjunction with the accompanying drawings, in which:
In any event, through the use of the patch array feed antenna 50, the use of an expensive and relatively mechanically-complex horn antenna is obviated. The design provides further benefits in that the patch array feed antenna 50 can be formed onto the same PCB 22 used in the transceiver for other purposes, as just noted, in effect combining the circuitry and antenna functions into a single substrate. Moreover, the transceiver is made sleeker in its profile, as no mechanical parts (aside from the dish 16) are made to protrude from the housing 14, hence reducing alignment problems and potential damage that might result from protruding mechanical parts.
The patch array feed antenna 50 as formed in an exemplary embodiment on the PCB 22 is shown in further detail in
The other circuitry needed for operation of the transceiver 40 (such as the oscillators, tuners, receivers, etc.) is represented generally by circuit block 53, as mentioned above. One exemplary integrated circuit in circuit block 53 is shown as integrated circuit 74, which might comprise the oscillator for example. As shown, the integrated circuit 74 is preferably a “bare die,” i.e., an unpackaged integrated circuit. As one skilled in the art will understand, the use of bare dies are preferable when operating at high frequencies such as 77 GHz, as packaging the integrated circuits can add unwanted parasitic capacitance and inductance. As shown in
In one embodiment, the integrated circuit 74 is placed in a hole 75 in the PCB 22, which can be milled in the PCB 22. This allows the integrated circuit to be conductively epoxied to the ground plane 73 under the PCB 22 to improve the grounding stability of the patch array feed antenna 50. Of course, the disclosed embodiment for mounting the integrated circuits 74 within circuit block 53 and for coupling the same to the common feed 67 are merely exemplary, and other means could be used as one skilled in the art will appreciate.
Once the PCB 22 is formed, care should be taken not to damage any exposed connections, such as the bond wires. Accordingly, the circuitry can be covered by a low-loss cap or lid to protect the components and connection, and/or appropriate recesses can be formed in the housing 14 to allow clearance for such components and connections. See, e.g., the above-incorporated patent application for further details. In one embodiment, the cap or lid can comprise the radome, discussed in further detail below. Such components may also be covered with a protective epoxy once formed, but this is less preferred as it might add additional capacitance and inductance to the circuitry and hamper performance.
The PCB 22 can also include a connector portion 51 suitable for connecting the PCB and its traces to an edge connector (not shown), which for example might couple to a vehicle communication bus (not shown). The various leads in the connector portion 51 would carry power, control and data (i.e., reflection data) between the PCB 22 and the vehicle in which the transceiver 40 is placed. For example, when a reflected signal is detected through its resonance of the antenna 50, that signal is preferably processed at circuit block 53 and causes a signal (i.e., indicator) to be sent to a lead or leads on the connector portion to inform the vehicle of the detected potential hazard. Such signal can then be sent by the vehicle communication bus to the control system of the vehicle, for example, to cause the vehicle to reduce its speed. Or, such signal might merely be audibly broadcast to a user of the vehicle (e.g., a “beep” or a warning voice message), or displayed to the user (e.g., a lit LED or an indication on an interface screen), or both. Alternatively, processing of the reflected signals can be performed off of the PCB 22.
Generally, radiation 20 will emit from each patch 60 orthogonal to its surface (i.e., straight upwards). See David M. Pozar, “Microwave Engineering,” published by Addison-Wesley, pp. 183–184 (1990), which is incorporated herein by reference. However, in a preferred embodiment, the patches 60 of the patch array feed antenna 50 provide the ability to “steer” the emitted or received beam of radiation 20. As can be best seen from
Accordingly, each of the patches 60 is laid out at slightly different distances or locations on the PCB 22. For example, consider traces 63a and 63b in
A cross section of the PCB 22 is shown in
Although a preferred embodiment is described, one skilled in the art of antenna physics will understand that the desired functionality of the patch array feed antenna 50 can be achieved in many different ways. The number of patches, their size, the nature in which they are arrayed, their respective distances, the materials used to form them, the frequencies at which they resonate, etc., can be easily varied to arrive at any number of variations. The antenna could be in the form of another well known planar antenna, such as a printed dipole, so long as the radiation pattern is perpendicular to the surface but has a wide beam suitable for steering at acute angles. Accordingly, none of these parameters is crucial, and the invention should not be understood as limited to any of these particulars as disclosed. Moreover, while particularly useful in the broadcast and detection of 77 GHz radiation, the disclosed patch array feed antenna 50 can be used with (and tailored for) other frequencies as well. For example, future transceiver assemblies may use even higher frequencies, such as 140 GHz, 220 GHz, or any other publicly available band, with the use of such higher frequencies allowing the antenna to be made smaller and/or more directive.
The overall construction of the vehicular collision detection transceiver 40 is likewise susceptible to various modifications. As shown in
A “patch” as used herein should be understood as referring to any planar element capable of radiating orthogonally to the substrate on which it is formed. Thus, a “patch” need not be strictly rectilinear is shape, but includes shapes such as lines, squares, rectangles, and other more complex shapes such as spirals or shapes containing notches capable of radiating orthogonally to the substrate. Consistent with this understanding, a “patch” should also be understood to refer to the absence of metallization, and can actually refer to a portion of a “slot antenna,” such as those that comprise a slot in the ground plane of a grounded substrate, including printed dipole antennas and microstrip traveling-wave antennas. See Ramesh Garg, “Microstrip Antenna Design Handbook,” published by Artech House, pp. 8–14 (2001), which is incorporated herein by reference.
While preferably disclosed as a having a parabolic reflector dish 16, one skilled in the art will understand that the disclosed transceiver 40 may be formed using other types of reflectors. For example, the dish 16 may be replaced by a “reflectarray,” which essentially constitutes a plurality of patches tuned to reflect radiation similarly to a parabolic antenna. See Pozar, “Design of Millimeter Wave Microsrtip Reflectarrays,” IEEE Transactions on Antennas and Propagation, Vol. 45, No. 2, pp. 287–296 (February 1997), which is incorporated herein by reference.
The disclosed antenna could also be designed for specific polarizations of the radiation 20, which is useful because some objects being detected might reflect certain polarizations differently. See Ramesh Garg, “Microstrip Antenna Design Handbook,” published by Artech House, pp. 493–497 (2001), which is incorporated herein by reference.
Although disclosed in the context of being useful within a vehicle, the disclosed transceiver assembly can be used in other contexts as well to detect the presence of objects other than those present while driving.
It should be understood that the inventive concepts disclosed herein are capable of many modifications. To the extent such modifications fall within the scope of the appended claims and their equivalents, they are intended to be covered by this patent.
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